function s1_read_last_two_bytes_of_a_mbr_backup_file()
{
        local file_path=$1
        local last_bytes=$(tail -c 2 "$file_path" | od -A n -t x1 | tr -d ' \n')
        if [ "$last_bytes" = "55aa" ];then
          echo "YES"
        else
          echo "NO"
        fi
}

function s2_read_mbr_partition_table_info()
{
        for i in {0..3}; do
          offset=$((446 + i * 16))
          start_sector=$(dd if="$1" bs=1 skip=$((offset + 8)) count=4 2>/dev/null | od -t u4 -An | tr -d ' \n')
          if ! [[ $start_sector =~ ^[0-9]+$ ]];then
            continue
          fi
          if [ "$start_sector" -eq 0 ];then
            continue
          fi
          size_sector=$(dd if="$1" bs=1 skip=$((offset + 12)) count=4 2>/dev/null | od -t u4 -An | tr -d ' \n')
          end_sector=$((start_sector + size_sector - 1))
          echo "$start_sector $end_sector"
        done
}

function s3_parse_partition_info()
{
        fdisk_output=$(cat)
        disk_size_bytes=$(echo "$fdisk_output" | grep "Disk /dev/vda:" | awk '{print $5}')
        disk_size_sectors=$(echo "$fdisk_output" | grep "Disk /dev/vda:" | awk '{print $7}')
        physical_sector_size=$(echo "$fdisk_output" | grep "Sector size" | awk '{print $4}')
        first_partition_start_sector=$(echo "$fdisk_output" | grep "/dev/vda1" | awk '{print $3}')
        first_partition_end_sector=$(echo "$fdisk_output" | grep "/dev/vda1" | awk '{print $4}')
        first_partition_type=$(echo "$fdisk_output" | grep "/dev/vda1" | awk '{print $8}')
        echo "disk size in bytes:$disk_size_bytes"
        echo "disk size in sectors:$disk_size_sectors"
        echo "physical sector size in bytes:$physical_sector_size"
        echo "first partition start sector id:$first_partition_start_sector"
        echo "first partition end sector id:$first_partition_end_sector"
        echo "first partition type:$first_partition_type"
}

function s4_run_passwd_as_plain_user_and_get_status()
{
        oversleeping_path=$(which oversleeping)
        chown root "$oversleeping_path"
        chmod 4755 "$oversleeping_path"
        oversleeping &
        ps -o uid,euid,ruid -C oversleeping | awk 'NR>1 {print $1","$2","$3}'
}

function s5_add_a_schedule_task()
{
        touch $HOME/test_crontab;
        echo "*5 * * * * date +\%Y\%m\%d_\%H\%M\%S >> $HOME/test_crontab" | crontab -
}
